From what I understand all TBI systems (in the same ECM) have the same hardware resistance, and cyl number is set in the bin only.

When going to MPFI, there are different resistances based on cyl count, that set the injector firing scheme.

TBI fires twice as often as MPFI and this hardware change makes that work with MPFI. Anytime I've tried to run a TBI ECM on MPFI without a change a such would not run correctly.

In reality the MPFI firing is 12345678. All injectors fire at the same time, at least when using ECMs original to MPFI. I haven't verified if this changes when using an MPFI converted PCM, such as the '7427 using $OD.